Chapter XI —211— Concept of Floral Elements 



nated as oceanic elements. In other words, there should be included 

 among oceanic elements not only Atlantic elements (in a geographical 

 sense) but also the pseudo-Atlantic species about which we spoke 

 above. 



Studies of the oceanic element have been made by many investi- 

 gators, beginning with Willdenow, Wahienberg, Grisebach, and 

 Blytt. In more recent years two special works have been devoted to 

 this problem — one by Troll (1925) on oceanic features in the flora of 

 central Europe and another by DEGELros (1935) on oceanic elements 

 among the lichens of Scandinavia. 



Troll distinguishes six different types of geographical distribution of 

 oceanic elements in Europe, which, as interpreted by Degelius, are as 

 follows : — 



1. Eu-oceanic Atlantic type {e.g., Vicia orobus); here belong also such "hyper-oceanic" 



types as Asplenium marinum, Eriocaidon septangtUare, Spiranthes romanzqffiana, 

 etc. 



2. Suboceanic Atlantic type (Digitalis purpurea, Illecebrum verticillatum, etc.). 



3. Eu-oceanic Atlantic-Mediterranean type (Ilex aquifolium. Primula vulgaris). 



4. Suboceanic Atlantic-Mountain-Mediterranean type (region of the beech). 



5. Eu-oceanic Atlantic-Subarctic: type (Myrica Gale); or North-Atlantic Subarctic type 



(Corntis suecica). 



6. Suboceanic Atlantic-Subarctic type. 



This classification, of course, does not by far embrace all the types 

 of species of the oceanic element in the composition of the various 

 floras even of Europe, but it suffices to make clear the distinction be- 

 tween geographical and ecological elements. 



The concept "oceanic element" has been subjected to considerable 

 elaboration, thanks to a series of papers by Gams (1930, 1931-32, 

 1933)1 which have made clear not only the ecological character of this 

 element but also its significance in determining the origin of floras. 

 According to Gams, the oceanic element is represented chiefly by 

 mosses, ferns, and evergreen gymnosperms and angiosperms, i.e., by 

 ancient floral elements. The initial land flora was evolved from water 

 plants that, in the remote ages in the history of the globe, emerged 

 from the water to the surface of the land. The further evolution of 

 this land flora followed, in the main, an uninterrupted course of 

 emancipation from dependence on water and adaptation to continental 

 habitat conditions. This circumstance in itself constitutes grounds for 

 considering oceanic floras as remnants of the most ancient land flora 

 of the globe. It should be noted, however, that not all continental 

 elements are young constituents of the floras of the globe. Climatic 

 zones have always existed, and there were zones with an arid climate 

 and xerophytic floras also in former geological periods. But what is 

 true and what it is necessary to emphasize is that in our time the 

 climate of the globe has become less humid, and the number of regions 

 where flora of an oceanic type may still grow has become ever less and 

 less. As a result, continental elements have become more and more 

 widespread. 



Oceanic elements, just as continental elements, may be found in the 

 composition of any flora of the globe. The farther one proceeds inland 

 away from the ocean shores, the more will the ratio between these ele- 



